Mark older documentation for PuppetDB 'unmaintained'

We have decided to stop maintaing documentation for versions 1.2 and older,
thus allowing us to kill off those branches.

This changes the include file to warn users older revisions of the docs are
unmaintained. It also changes our index page for the same effect.

Signed-off-by: Ken Barber <ken@bob.sh>
Point PuppetDB 1.1/1.2 directly at their refs so we can clear the branches

In case we want to clear the branches in the future, this points the docs at
the latest sha1 hashes for each branch at the point of declaring the docs
'unmaintained'.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #210 from kbarber/frozen_docs_warning_for_puppetdb_pre13

Mark older documentation for PuppetDB 'unmaintained'